A medium-duty diesel engine has low power but no diagnostic trouble codes. Which check should the technician perform FIRST?
General Engine Diagnosis
Question · Easy
Technician A says blue exhaust smoke usually indicates oil consumption. Technician B says black exhaust smoke usually indicates incomplete combustion or excess fuel. Who is correct?
Chapter 1: General Engine Diagnosis: Symptoms & Verification
1.1 Diagnostic Strategy, Complaint Verification & SAE J1939 Fault Codes
Study guide
White smoke from a diesel exhaust during a cold start that clears as the engine warms is MOST likely caused by:
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During a cylinder cutout (kill) test on an electronically controlled diesel, the engine RPM does NOT drop when one cylinder is disabled. This indicates that cylinder is:
Question · Medium
A diesel engine is hard to start when cold but starts normally when warm. Glow systems are not used on this engine. Which is the MOST likely cause?
When performing a cylinder compression test on a medium/heavy diesel, the engine should be:
1.2 Exhaust Smoke Color, Odor & Misfire Symptom Diagnosis
An engine has excessive crankcase blowby. This condition is MOST directly an indicator of:
A diesel engine surges at idle. Technician A says air in the fuel system can cause idle surge. Technician B says a sticking fuel control actuator or faulty rail pressure control can cause idle surge. Who is correct?
The BEST tool for locating an internal coolant-to-oil leak before disassembly is:
Question · Hard
An engine knocks under load. Which of the following is the LEAST likely cause of the knock?
1.3 Hard-Start, No-Start & Engine Derate Diagnostic Protocols
An accurate way to confirm a no-start is fuel-related rather than electrical on an electronic diesel is to:
A heavy-duty diesel has an intermittent miss under light load. The MOST efficient diagnostic approach is to:
Coolant in the engine oil that produces a milky brown appearance on the dipstick MOST likely indicates:
A used-oil analysis report shows high silicon. This MOST likely indicates:
1.4 Engine Noise & Vibration Isolation and Diagnosis
An engine consumes excessive fuel and produces black smoke under load but boost pressure is below specification. The MOST likely cause is:
Before condemning an electronic engine sensor as the cause of a driveability complaint, the technician should FIRST:
A diesel engine runs but lacks power and the ECM shows it is in a derate (limp) mode. The technician should:
Fuel found in the engine oil (rising oil level, fuel smell) on a common-rail engine is MOST likely caused by:
Chapter 2: General Engine Diagnosis: Mechanical & Fluid Testing
2.1 Compression, Cylinder Leakage & Crankcase Blowby Testing
Technician A says low compression in one cylinder can cause that cylinder to misfire and produce white smoke. Technician B says low compression should be confirmed with a cylinder cutout or compression test before head removal. Who is correct?
An engine has high oil consumption with no external leaks and blue exhaust smoke. The MOST likely diagnostic conclusion is:
A cylinder head is checked for flatness. The straightedge and feeler gauge reveal warpage exceeding the manufacturer limit. The correct action is to:
Cylinder Head Valve Train
Excessive valve stem-to-guide clearance on a diesel will MOST likely cause:
2.2 Electronic Cylinder Cutout & Relative Compression Contribution Testing
When adjusting valve lash on a heavy-duty diesel, the valve being set must be:
Technician A says insufficient valve lash can cause a valve to be held off its seat and burn. Technician B says excessive valve lash can cause a clicking noise and valvetrain damage. Who is correct?
A diesel cylinder head shows cracks between the valve seats. The MOST appropriate evaluation method is:
A bent or worn rocker arm on a diesel valvetrain will MOST likely result in:
2.3 Used Oil Spectroscopy, Physical Fluid Contamination & Coolant Intrusion
After resurfacing a diesel cylinder head, the technician must verify:
An engine block deck surface is inspected before reassembly. The PRIMARY reason is to:
Engine Block
On a wet-sleeve diesel engine, insufficient cylinder liner protrusion above the deck will MOST likely cause:
Cylinder bore measurements show taper and out-of-round beyond the wear limit on a parent-bore (non-sleeved) block. The correct repair is to:
Chapter 3: Cylinder Head & Valve Train Diagnosis & Repair
3.1 Cylinder Head Flatness, Crack Inspection & Surface Resurfacing
Excessive crankshaft end play measured with a dial indicator MOST likely indicates:
Plastigage is used during diesel engine assembly primarily to measure:
Technician A says a cracked cylinder block can be confirmed by pressure-testing the coolant passages. Technician B says a porous or cracked block can sometimes be detected by magnetic particle inspection on ferrous material. Who is correct?
During reassembly, connecting rod bolts that are torque-to-yield (stretch) type should be:
3.2 Valve Guides, Stem-to-Guide Clearance, Seats & Springs
A scored cylinder liner with vertical scratches and metal transfer is MOST commonly caused by:
A piston that shows a hole melted through the crown is MOST often the result of:
When honing a cylinder, the correct crosshatch pattern is important because it:
Low engine oil pressure at idle while pressure is acceptable at higher RPM MOST likely indicates:
Lubrication Cooling
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